The human eye contains a natural crystalline lens that focuses light on the retina. The lens may become cloudy, forming a cataract, which makes it impossible to see clearly. When the cataract progresses and vision becomes greatly hindered, cataract surgery becomes necessary. This procedure removes the natural lens and replaces it with an implantable medical device called an intraocular lens (IOL). The IOL is an artificial lens conventionally made of plastic, silicone, or acrylic and performs the function of a normal lens. Current IOLs are made of soft materials, allowing them to be folded and implanted in the eye with a small incision. Standard IOLs are monofocal, providing a set focal point.
IOL implantation has become the standard of care after cataract extractions. Most IOLs are made of single piece of hard material, although some newer IOLs have a two-lens design, and lenses filled with clear fluid have also been proposed. Most current IOLs are prefabricated for their lens power and then placed in the eye, but again, a few designs involve intraocular filling of the liquid in the lens at the time of initial surgery or possibly at a subsequent time (e.g., for adjustment or should the liquid become opacified, or even simply to refill the liquid in the lens). A liquid-filled bag that provides accommodation—made from, for example, an elastic, biocompatible polymer—results in numerous benefits and advantages, e.g., the ability to adjust the lens following implantation; to customize the lens to the needs of each patient; to accommodate vision; sharper vision over a wide range of distances; and reduction of visual side effects such as glares and halos. See, e.g., U.S. Pat. No. 8,038,711, the entire disclosure of which is hereby incorporated by reference.
Tailoring a fillable IOL to the ocular needs and anatomy of a particular patient requires detailed knowledge of the implantation site and the response of the lens as it is filled. Although there exist approaches to measure the overall refractive power of an eye with implantable lenses at the time of surgery (before or after IOL implantation) and also in the perioperative period, we are aware of no biometric methods for guiding the refractive power of an IOL that is filled with liquid during initial surgery or at subsequent time periods.